I've been using windows 7 for about 3 weeks now. I haven't encountered any problems with the extensions I've used. Either WebAssists or others.
The problem that was experienced in DreamWeaver itself however is still there. This is nothing to do with extensions at all but with DW itself. In Vista and now still in Win 7, there is a problem with defining paths to folders using the DW folder icon to browse to it. It always falsl one short of the folder you want.
Anyway, as I say that's not extension specific, it happens when you define a site for example.
So far WebAssist has the thumbs up from me as far as win7 compatibility is concerned.